text: /* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 4 -*-
   * This Source Code Form is subject to the terms of the Mozilla Public
   * License, v. 2.0. If a copy of the MPL was not distributed with this
   * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
  
  #ifndef GFX_FT2UTILS_H
  #define GFX_FT2UTILS_H
  
  #include "cairo-ft.h"
  #include "gfxFT2FontBase.h"
  #include "mozilla/Likely.h"
  
  // Rounding and truncation functions for a FreeType fixed point number 
  // (FT26Dot6) stored in a 32bit integer with high 26 bits for the integer
  // part and low 6 bits for the fractional part. 
  #define FLOAT_FROM_26_6(x) ((x) / 64.0)
  #define FLOAT_FROM_16_16(x) ((x) / 65536.0)
  #define ROUND_26_6_TO_INT(x) ((x) >= 0 ?  ((32 + (x)) >> 6) \
                                         : -((32 - (x)) >> 6))
  
  typedef struct FT_FaceRec_* FT_Face;
  
  class gfxFT2LockedFace {
  public:
      explicit gfxFT2LockedFace(gfxFT2FontBase *aFont) :
          mGfxFont(aFont),
          mFace(cairo_ft_scaled_font_lock_face(aFont->CairoScaledFont()))
      { }
      ~gfxFT2LockedFace()
      {
          if (mFace) {
              cairo_ft_scaled_font_unlock_face(mGfxFont->CairoScaledFont());
          }
      }
  
      FT_Face get() { return mFace; };
  
      /**
       * Get the glyph id for a Unicode character representable by a single
       * glyph, or return zero if there is no such glyph.  This does no caching,
       * so you probably want gfxFcFont::GetGlyph.
       */
      uint32_t GetGlyph(uint32_t aCharCode);
      /**
       * Returns 0 if there is no variation selector cmap subtable.
       */
      uint32_t GetUVSGlyph(uint32_t aCharCode, uint32_t aVariantSelector);
  
      void GetMetrics(gfxFont::Metrics* aMetrics, uint32_t* aSpaceGlyph);
  
      // A scale factor for use in converting horizontal metrics from font units
      // to pixels.
      gfxFloat XScale()
      {
          if (MOZ_UNLIKELY(!mFace))
              return 0.0;
  
          const FT_Size_Metrics& ftMetrics = mFace->size->metrics;
  
          if (FT_IS_SCALABLE(mFace)) {
              // Prefer FT_Size_Metrics::x_scale to x_ppem as x_ppem does not
              // have subpixel accuracy.
              //
              // FT_Size_Metrics::x_scale is in 16.16 fixed point format.  Its
              // (fractional) value is a factor that converts vertical metrics
              // from design units to units of 1/64 pixels, so that the result
              // may be interpreted as pixels in 26.6 fixed point format.
              return FLOAT_FROM_26_6(FLOAT_FROM_16_16(ftMetrics.x_scale));
          }
  
          // Not scalable.
          // FT_Size_Metrics doc says x_scale is "only relevant for scalable
          // font formats".
          return gfxFloat(ftMetrics.x_ppem) / gfxFloat(mFace->units_per_EM);
      }
  
  protected:
      /**
       * Get extents for a simple character representable by a single glyph.
       * The return value is the glyph id of that glyph or zero if no such glyph
       * exists.  aExtents is only set when this returns a non-zero glyph id.
       */
      uint32_t GetCharExtents(char aChar, cairo_text_extents_t* aExtents);
  
      typedef FT_UInt (*CharVariantFunction)(FT_Face  face,
                                             FT_ULong charcode,
                                             FT_ULong variantSelector);
      CharVariantFunction FindCharVariantFunction();
  
      RefPtr<gfxFT2FontBase> mGfxFont;
      FT_Face mFace;
  };
  
  #endif /* GFX_FT2UTILS_H */
  